Photographic development

ABSTRACT

Photographic silver halide elements are described which comprise incorporated in a silver halide emulsion layer or another waterpermeable colloid layer a hydroquinone silver halide developing agent precursor of which at least one of the hydroxyl groups of said hydroquinone has been esterified to form a hydrolyzable aliphatic acyloxy radical comprising a quaternary ammonium group. Upon treatment of the exposed elements with an alkaline solution the developing agent precursor hydrolyzes readily to yield the active developing agent so that no delay in development occurs. The resulting developed images are free from spots, do not show fog and possess the desired sensitivity and gradation with normal or even shorter length of development time.

United States Patent Willems et al.

[ 51 Mar. 21, 1972 [54] PHOTOGRAPHIC DEVELOPMENT [73] Assignee: Gevaert-AGFA N.V., Mortsel, Belgium [22] Filed: May 23, 1969 [21] Appl. No.: 827,145

[30] Foreign Application Priority Data June 10, 1968 England ..27,524/68 [52] US. Cl ..96/66, 96/95 [51] ..G03c 5/30 [58] Field of Search ..96/29, 66

[56] References Cited UNITED STATES PATENTS 3,039,869 6/l962 Rogers et al. ..96/66 l-lD 3,113,026 12/1963 Sprung ..96/66 Primary ExaminerNorman G. Torchin Assistant ExaminerJohn L. Goodrow Attorney-Alfred W. Breiner 57 ABSTRACT Photographic silver halide elements are described which comprise incorporated in a silver halide emulsion layer or another water-permeable colloid layer a hydroquinone silver halide developing agent precursor of which at least one of the hydroxyl groups of said hydroquinone has been esterified to form a hydrolyzable aliphatic acyloxy radical comprising a quaternary ammonium group. Upon treatment of the exposed elements with an alkaline solution the developing agent precursor hydrolyzes readily to yield the active developing agent so that no delay in development occurs. The resulting developed images are free from spots, do not show fog and possess the desired sensitivity and gradation with normal or even shorter length of development time.

12 Claims, No Drawings PHOTOGRAPHIC DEVELOPMENT The present invention relates to photographic materials and to a method of developing said materials. More particularly the present invention relates to photographic materials having incorporated therein photographic developing agents and to a method of processing and using the same.

An exposed photographic element comprising a support having at least one silver halide emulsion layer thereon is commonly developed by means of a developing solution comprising a silver halide developing agent. This developing solution after having been used for some time becomes less efficient among other reasons by aerial oxidation so that it should be frequently replenished or replaced, particularly when no or little preservative such as sodium sulphite is present in the said developing solution.

In order to overcome these inconveniences it is known to incorporate developing agents into the photographic material itself and to initiate development of the exposed material by treatment with alkaline solutions. However, due to the presence of reducing functions said developing agents have an adverse influence upon the silver halide emulsion, particularly high-sensitive emulsions. Therefore it has been proposed to incorporate the developing agent under a chemically masked form into the photographic material. For instance, it has been proposed to incorporate an organic or a substantially water-insoluble inorganic ester of a polyhydroxy benzene compound in at least one colloid layer of the photographic material. Although these so-ealled developer precursor compounds have a high stability in the emulsion layer and the absence of reducing functions in their molecule whereby any marked adverse influence upon the light-sensitive silver halide emulsion is excluded, they show the disadvantage of being hydrolyzed very slowly in the alkaline activating bath so that a delay in release of active developer and thus in development is involved.

In United States Pat. No. 3,246,988 of Ralph F. Porter, Thomas E. Gompf, issued Apr. 19, 1966 it has been proposed to use as developer precursor compound for incorporation into a photographic light-sensitive material halogenated esters of 1,4-dihydroxy benzene compounds. These halogenated esters of 1,4-dihydroxy benzene compounds show the advantage over unsubstituted esters of the said compounds of being more rapidly hydrolyzed in the alkaline activating bath.

It has now been found that hydroquinone compounds wherein at least one of the hydroxyl groups has been esterified to form a hydrolyzable aliphatic acyloxy group comprising a quaternary ammonium substituent are very effective developing agent precursors for use in light'sensitive silver halide material, which hydrolyze in an alkaline activator bath to release the active developer even more rapidly than the corresponding haloacyloxy compounds.

The invention in its broadest aspect consists of the said hydroquinone compound. Also in accordance with the invention a photographic element is provided comprising a support and at least one light-sensitive silver halide emulsion layer and integral with said photographic element, e.g., in a light-sensitive emulsion layer and/or in a colloid layer in water-permeable relationship therewith a hydroquinone developing agent precursor wherein at least one of the hydroxyl groups of said hydroquinone compound has been esterified to form a hydrolyzable aliphatic acyloxy radical comprising a quatemary ammonium group. The benzene ring of the hydroquinone compounds can contain any of the conventional substituents such as alkyl (e.g., methyl, ethyl, t-butyl, N-hexyl, n-octyl, etc.) and halogen e.g., chlorine, bromine, etc.).

The novel hydroquinone silver halide developing agent precursors of use according to the present invention can be represented more particularly by the following general formula:

A0 O-E-X-O wherein Y stands for hydrogen or one or more substituents selected from alkylsuch as methyl, ethyl, t-butyl, etc. and halogen such as chlorine, bromine,

X stands for methylene or ethylene including methylene or ethylene substituted by alkyl or aryl,

Q stands for an ammonium group of one of the formulas M stands for chlorine or bromine,

each of R and R stands for an alkyl group or an aralkyl group or together represent the atoms necessary for completing a heterocyclic ring, e.g., morpholine, pyrrolidine and piperidine,

R stands for an alkyl group or an aralkyl group,

R, stands for an alkylene group, and

Z represents the atoms necessary to close a heterocyclic nucleus such as pyridine,

A stands for hydrogen or the group By the term hydroquinone silver halide developing agent precursor is to be understood a developing agent having no developing action before the development is actually desired; when this developer precursor compound is treated with aqueous baths, particularly with an alkaline aqueous bath the ester group(s) is (are) split off by hydrolysis and the original, actual hydroquinone developing agent is set free.

The present invention also provides a process for developing a photographic silver image in a silver halide emulsion layer by incorporating in said emulsion layer and/or in a col loid layer in waterpermeable relationship with said emulsion layer, e.g., an undercoat or overcoat for such emulsion layer, a developer precursor compound as defined above and by carrying out the development by means of an alkali solution.

ln the presence of aqueous alkali, the developer precursor compounds of the invention hydrolyze readily to yield the corresponding active hydroquinone silver halide developing agents so that no delay in development is involved. Indeed, the quaternary ammonium group accelerates hydrolysis of the ester group. Moreover, the images obtained are free from spots, do not show fog or defects caused by desensitization and possess the desired sensitivity and gradation with normal length or even shorter length of development time.

The developer precursor compounds of the invention are better water-soluble than unsubstituted esters or halogenated esters of 1,4-dihydroxy benzenes and thus need not be incor porated in the photographic material in dispersed form. By the presence of the quaternary nitrogen atom the compounds of the invention can be absorbed to the silver halide grains thus creating very favorable circumstances for rapid development. It would appear that they have the same favorable development action as in the case when using hydroquinone and quaternary ammonium compounds separately. 7

Representative developing agent precur sbrcompound s ac cording to the present invention and corresponding to the above general formula are Melting e;

1 O C1H5 215 noQ-o-ii-cm-n'v-mm 01- 2 O (CHgh-CH; 215

no-Q-o-r'i-om-oi-(0119mm, Cl-

( I): Ha

a (Gibb-CH; 195

no-Q-o-ii-om-nL-wmn-om c- (emu-CH.

4 o cam-0H, 13s

HOQO--CHr-flL-(Cfiflt-CH; c1-

((|JH:)4CH:

a 0 on, 120

H00( 5CHg+I I-(GEM- 01' noQo-r'i-om-nL-cm-Q c1- O I CHr-CH: ao-Q-o-r'i-cm-u/ c1- CH1C7 HOQ-o-r'i-CEh-M 01- noQ-o-c'i-om-flf (CH:)|CH| 01- Ho-oi-cm+1 I-(om)r-+i z-om-ii-o--orr 201- 11 o 0 12a noQ-o-tkom-uf (OH,), \v-om-d-oQ-on 201- 12 Calls 0 0 0,11, 260

Hm-w-cH+iio-o :-cm+1 1c,m 201- As is illustrated by some preparations hereinafter, the development precursor compounds according to the present invention can be prepared by reaction of the corresponding haloacyl monoesters or diesters with compounds of the following formulas 1 to 4:

BiN (1) wherein R R R R, and Z have the same significance as given above. When the haloacyl esters are allowed to react with compounds of formulas (l) and (3) the said compounds PREPARATION l :COMPOUND l To a solution of 37.3 g. (0.2 mole) of the chloroacetyl monoester of hydroquinone in 200 ml. of acetone 40 ml. (0.28 mole) of triethylamine are added. The mixture is refluxed for 6 hours and the precipitate formed is filtered by suction and washed with water.

are used in amounts exceeding those of the haloacyl esters Yi ld; 37 g. (65 Melting point 215 C.

suction and washed with acetone. Yield 37 g (64 Melting point 220 C.

PREPARATION 3 COMPOUND 8 To a solution of 37.3 g. (0.2 mole) of the chloroacetyl monoester of hydroquinone in 200 ml. of acetone 24 g. (0.3 mole) of pyridine are added. The mixture is refluxed for 6 hours with stirring whereupon the oily precipitate is separated. The product is purified by pouring a methanolic solution thereof into ether.

Yield: 18 g. (34 Melting point: 210 C.

PREPARATION 4 1 COMPOUND 10 To a solution of 56 g. (0.3 mole) of the chloroacetyl monoester of hydroquinone in 500 m1. of acetone a solution of 21.75 g. (0.125 mole) of 1,6-bis(dimethylamino) hexane in 50 ml. of acetone is added dropwise with stirring. The mixture is refluxed for 2 hours and the precipitate formed is filtered off and purified by boiling in acetonitrile.

Yield 52.5 g. (77 Melting point 230 C.

PREPARATION 5 COMPOUND 12 To a solution of 52.6 g. (0.2 mole) of the chloroacetyl diester of hydroquinone in 200 ml. of acetone 60.6 g. (0.6 mole) of triethylamine are added. The mixture is stirred for 6 hours at room temperature and then left standing overnight. The precipitate formed is filtered by suction and purified by pouring an ethanolic solution thereof into ether.

Yield 47 g (50 Melting point: 260 C.

The developer precursor compounds of use according to. the present invention can be incorporated in a photographic silver halide emulsion suitable for preparing a light-sensitive silver halide emulsion layer of a photographic element or into a colloidal dispersion of a water-permeable hydrophilic colloid suitable for preparing a colloid layer in water-permeable relationship with a light-sensitive silver halide emulsion layer; of a photographic element, e.g., an undercoat or overcoat for such emulsion layer. I

The developer precursor compounds of the invention can be incorporated into said silver halide emulsion or into said colloidal dispersion by mixing a solution of the precursor compound in a suitable solvent, preferably water, with the said silver halide emulsion or the said colloidal dispersion prior to coating. When incorporating the developer precursor into a silver halide emulsion, the solution of said developer precursor may be added during no matter what step of emulsion preparation and preferably just before coating of the emulsion. The solution of the developing agents may also first be homogeneously admixed with a hydrophilic colloid composition, e.g., aqueous gelatin whereupon the whole is mixed with the photographic emulsion. 4

The concentration of developer precursor according to the present invention will vary markedly depending upon the particular chemical compound involved, the particular process in which the photographic element is to be used, and the location of the compound within the photographic element. When incorporated in the silver halide emulsion layer the amount of development precursor according to the present invention per rhble of sflver halide is generally such that upon treatment with the activator solution from 0.1 mole to 4 moles, preferably from 0.25 mole to 2 moles, of hydroquinone are set free. When incorporated in another colloid layer which is in contact with or which will come into contact with the silver halide emulsion layer on development somewhat larger concentrations can be used.

The photographic elements of the present invention comprising a photographic development precursor compound either in a photographic silver halide emulsion layer and/or in another colloid layer in water-permeable relationship with the said emulsion layer can be developed, after exposure, by means of a mere alkaline activator bath. These alkaline activator baths for development of the photographic element incorporating the developing agents according to the present invention, can be of different composition. Although a simple solution of an alkaline material, e.g., an aqueous solution of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, borax, etc., will suffice, it may be advisable to add some other additives such as wetting agents, preserving agents such as sodium sulphite, activators, silver halide solvents, superadditive developing agents, etc.

The activator solutions may be applied to an exposed photographic element according to the present invention in any known way such as by dipping, spraying, etc.

The photographic element developed according to the present invention can be stabilized by conventional fixation or by stabilization. As a matter of fact the developing agent precursors of the invention are particularly suitable for use in photographic elements intended for stabilization processing, which elements preferably comprise developing agents so that the developing bath can be limited to a mere activator bath. For more details about stabilization processing there can be referred to A. A. Newman The Chemistry of stabilization processing," The British Journal of Photography Nov. 1967, p. 1,009 and the literature cited therein.

The photographic silver halide emulsions of use according to the present invention may be of any type, e.g.. spectrally sensitized and non-sensitized emulsions, X-ray emulsions and emulsions sensitive to infra-red radiation. They may be highsensitive negative emulsions as well as rather low sensitive positive emulsions. The emulsions may be orthochromatic or panchromatic.

Various silver salts may be used as light-sensitive salt, e.g., silver bromide, silver iodide, silver chloride or mixed silver halides, e.g., silver chloro-bromide or silver bromoiodide.

The silver halides are dispersed in the common hydrophilic colloids such as gelatin, casein, polyvinyl alcohol, carboxymethylcellulose, sodium alginate, etc., gelatin being however favored.

The light-sensitive emulsions may be chemically as well as optically sensitized. They may be chemically sensitized by effecting the ripening in the presence of small amounts of sulphur containing compounds such as allyl thiocyanate, allyl thiourea, sodium thiosulphate, etc. The emulsions may also be sensitized by means of reducing agents for instance tin compounds as described in French Pat. No. 1,146,955 filed Apr.

'1 1, 1956, by Gevaert Photo-Producten N.V., Belgian Patent No. 568,687 filed June 18, 1958 by Gevaert Photo-Producten N.V. and in U.S. Pat. No. 2,487,850 of Burt H. Carroll issued Nov. 15, 1949, imino-amino methane sulphinic acid compounds as described in British Patent No. 789,823 filed Apr. 29, 1955 by Gevaert Photo'Producten N.V. and small amounts of noble metal compounds such as gold, platinum, palladium, iridium, ruthenium and rhodium. They may be optically sensitized by means of cyanine and merocyanine dyes.

It is evident that other additives such as development accelerators, anti-fogging agents, stabilizers, sensitizers, anti-oxidizing agents, may also be incorporated into the composition of the silver halide emulsion layer or other water-permeable colloid layer.

Examples of development accelerators which may be added to the emulsion layer or other water-permeable colloid layer are the polyoxyalkylene derivatives such as those described in U.S. Pat. Nos. 2,531,832 of William Alexander Stanton, issued Nov. 28,-1950, 2,533,990 of Ralph Kingsley Blake issued Dec. 12, 1950, 3,210,191 of.1.Willems, .1. De Munck, and R. Thiers issued Oct. 5, 1965 and 3,158,484 of J. Willems, R. Thiers and J. De Munck issued Nov. 24, 1964 and in United Kingdom Pat. Nos. 920,637 filed May 7, 1959 by Gevaert Photo-Producten N.V., and 991,608 filed June 14, 1961 by Kodak Co., as well as the amino-N-oxides as described in United Kingdom Pat. No. 1,121,696 filed Oct. 7, 1965 by Gevaert-Agfa N.V.

Examples of stabilizers and antifoggants are heterocyclic nitrogen containing thioxo compounds such as benzothiazoline-Z-thione and 1-phenyl-2-tetrazoline-5-thione and particularly compounds of the hydroxytriazolopyrimidine type (azaindolizines). The emulsions may further be stabilized with mercury compounds. Suitable mercury compounds are for instance the mercury compounds described in Belgian Pat. Nos. 524,121, filed Nov. 7, 1953 by Kodak Co., 677,337 filed Mar. 4, 1966 and 707,386 filed Dec. 1, 1967 both by Gevaert-Agfa N.V., and in U.S. Pat. No. 3,179,520 of Yoshio Miura, Akira Kiumai and Yosuke Nakajima issued Apr. 20, 1965.

The stabilizers, antifoggants and development accelerators may also be present in the alkaline activator solution.

The developer precursor compounds according to the present invention can also be used in combination with other auxiliary developing agents present either in the photographic element like the precursor compounds or in the activator solution. Typical auxiliary developing agents include 1-phenyl-3- pyrazolidinone and derivatives such as l-p-tolyl-3- pyrazolidinone, l-phenyl-5-methyl-3-pyrazolidinone, l-phenyl-4,4-dimethyl-3-pyrazolidinone, l-acetamidophenyl-3- pyrazolidinone, etc.

The developer precursors of the present invention can be used in the light-sensitive material and/or in the image-receiving material used in the application of the silver complex diffusion transfer process, the principle of which is described in United Kingdom Pat. Nos. 614,155 filed Nov. 2, 1939 and 654,630 filed Sept. 4, 1946 both by Gevaert Photo-Producten N.V. and in German Pat. No. 887,733 filed Jan. 24, 1941 by Agfa A.G.

For more details concerning the silver complex diffusion transfer process, the different embodiments of the materials and apparatus used therein, there can be referred to Process in Photography" 1955-1958, pp.2436 and the patent literature cited therein. In the silver complex diffusion transfer process it may also be advantageous to use in addition to the development precursors of the invention auxiliary developers which may be present in the said image-receiving material and/or light-sensitive material and/or the treating bath.

The activator solutions which are used in accordance with the present invention are stable for extended periods of time and not subject to decomposition reactions so common to conventional photographic developing solutions when storing these. No special precautions are required to prevent oxidation of the activator solutions since they are inherently quite stable.

The following examples will serve to illustrate the use of the development precursors according to the present invention.

EXAMPLE 1 An ordinary gelatino silver chloride emulsion was prepared and divided into ten aliquot portions. To these ten aliquot emulsion portions were added separately at a concentration of 0.65 mole per mole of silver chloride hydroquinone, pchloroacetoxyphenol, 1,4-bis(chloro-acetoxy)benzene, compounds 1, 3, 5, 7, and 8 and at a concentration of 0.325 mole per mole of silver halide compounds 10 and 11. The ten emulsions were then coated separately on ordinary photographic film supports and dried.

The elements obtained were exposed and developed by immersing them in a bath of the following composition potassium bromide l g.

anhydrous sodium sul hite 30 g. anhydrous sodium carbonate 30 g. water to make 1,000 ml.

The elements comprising p-chloroacetoxyphenol and 1,4- bis(chloroacetoxy)benzene showed no visible image after 60 sec. of development and the element comprising hydroquinone only a very faint image after 60 sec. of development. The elements comprising compounds 1, 3, 7 and 8 showed a faint image already after 20 sec. and a very good image after 60 sec. of development. The elements comprising compounds 5 and 10 showed a faint image already after 5 sec. of development and an excellent image after 30 seconds of development. Finally, the element comprising compound 1 1 showed a very good image already after 5 sec. of development and an excellent image after 20 sec. of development.

From this example it clearly appears that the development precursors of the present invention have marked advantages over the halogenated acyl esters of hydroquinone and over hydroquinone itself.

From a comparison of the results obtained there cannot only be concluded that the ammonium compounds hydrolyzed more rapidly in the alkaline treating bath than the corresponding halogenated acyl esters but moreover that the ammonium compounds act as developments accelerators (compare the results obtained with hydroquinone itself and those obtained with the compounds of the invention).

EXAMPLE 2 Two photographic elements A and B were prepared in an analogous way as the photographic elements of Example 1, using as development precursorszcompound l2 and 1,4-bis (chloroacetoxy)benzene respectively at a concentration of 0.65 mole per mole of silver halide.

The two elements were exposed and developed by immersing them in a bath of the following composition potassium bromide l g.

borax 25 g. anhydrous sodium sulphite 25 g. 1-phenyl-3-pyrazolidinone 200 mg. water to make 1 liter Element A showed an excellent image after a development time of 30 seconds whereas element B showed only a faint image even after 60 seconds of development which shows that the dihaloacyl esters of hydroquinone are very slowly hydrolyzed as compared with corresponding compounds according to the present invention.

EXAMPLE 3 A conventional gelatino silver chlorobromide emulsion for stabilization processing (60 mole percent of silver bromide and 40 mole percent of silver chloride) comprising the common emulsion addenda was divided into three aliquot portions A, B and C. To these aliquot portions were added separately per mole of silver halide 0.65 mole of hydroquinone, 0.65 mole of compound 1 and 0.325 mole of compound 10 respectively. The emulsion portions were then coated separately on conventional baryta-coated paper supports and dried.

The elements obtained were exposed and developed by means of the following activator solution anhydrous sodium sulphite 25 g. anhydrous sodium carbonate 40 g. potassium bromide l g. water to make L000 ml.

After a development time of 5 min. element A showed no visible image whereas element B showed an image with maximum density 0.30 and element C an image with maximum density= 2.

When identical photographic elements A, B" and Cwere developed, after exposure by means of an activator solution comprising in addition to the above ingredients mg. of lphenyl-3-pyrazolidinone normal sensitometric results were obtained with all elements A, B and C. However, when storing the developed elements for 5 days at 57 C. and 36 percent 5i relative humidity the maximum density of the image of element A was markedly reduced whereas the images of elements B and C remained practically unchanged.

We claim:

1. A photographic element comprising a support and at least one silver halide emulsion layer, wherein said element comprises in the said emulsion layer and/or in a colloid layer in water-permeable relationship with the said emulsion layer a hydroquinone silver halide developing agent precursor of which at least one of the hydroxyl groups of said hydroquinone has been esterified to form a hydrolyzable aliphatic acyloxy radical comprising a quaternary ammonium group.

2. A photographic element according to claim 1, wherein said hydroquinone silver halide developing agent precursor corresponds to the general formula wherein Y stands for hydrogen or one or more substituents selected from alkyl and halogen, X stands for methylene or ethylene including methylene or ethylene substituted by alkyl or aryl, Q stands for an ammonium group of one of the formulas wherein M stands for chlorine or bromine,

each of R and R stands for an alkyl group or an aralkyl group or together represent the atoms necessary for completing a heterocyclic ring,

R stands for an alkyl group or an aralkyl group,

R stands for an alkylene group, and

2 represents the atoms necessary to close a heterocyclic nucleus,

A stands for hydrogen or the group 3. A photographic element according to claim 1, which comprises in addition to the said developing agent precursor an auxiliary photographic developing agent.

4. A photographic element according to claim 3, wherein said auxiliary developing agent is a l-aryl-3-pyrazolidinone developing agent.

5. A photographic element according to claim 4, wherein said l-aryl-3-pyrazolidinone developing agent is l-phenyl-3- pyrazolidinone.

6. Image-receiving material for use in a silver complex diffusion transfer process comprising an image-receiving layer and containing in a water-permeable layer a hydroquinone developing agent precursor of which at least one of the hydroxyl groups of said hydroquinone has been esterified to form a hydrolyzable aliphatic acyloxy radical comprising a quaternary ammonium group.

7. A process for forming a visible photographic image comprising treating an exposed photographic element as claimed in claim 1 with an alkaline solution.

8. A processfor forming a visible photographic image comprising treating an exposed photographic element according to claim 1, with an alkaline solution comprising an l-aryl-3- pyrazolidinone developing agent.

9. A process according to claim 7, wherein said alkaline solution is an alkaline solution comprising at least one compound selected from sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and borax.

10. A process for forming a visible photographic image ac cording to the silver complex diffusion transfer process according to which a positive image of an original is obtained by development of an image-wise exposed light-sensitive silver halide material and diffusion of the non-developed complexed silver halide from the emulsion layer of said material to an image-receiving material where the complexed silver halide is converted into a silver containing image in the presence of development nuclei or substances capable of forming such nuclei characterized in that said light-sensitive silver halide material and/or the said image-receiving material comprises a hydroquinone developing agent precursor of which at least one of the hydroxyl groups of said hydroquinone has been esterified to form a hydrolyzable aliphatic acyloxy radical comprising a quaternary ammonium group and in that development is effected by means of an alkaline solution.

11. A process according to claim 10, wherein said process is carried out in the presence of an l-aryl-3-pyrazolidinone developing agent.

12. A process according to claim 10, wherein said alkaline solution is an alkaline solution comprising at least one compound selected from sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and borax. 

2. A photographic element according to claim 1, wherein said hydroquinone silver halide developing agent precursor corresponds to the general formula : wherein : Y stands for hydrogen or one or more substituents selected from alkyl and halogen, X stands for methylene or ethylene including methylene or ethylene substituted by alkyl or aryl, Q stands for an ammonium group of one of the formulas :
 3. A photographic element according to claim 1, which comprises in addition to the said developing agent precursor an auxiliary photographic developing agent.
 4. A photographic element according to claim 3, wherein said auxiliary developing agent is a 1-aryl-3-pyrazolidinone developing agent.
 5. A photographic elemEnt according to claim 4, wherein said 1-aryl-3-pyrazolidinone developing agent is 1-phenyl-3-pyrazolidinone.
 6. Image-receiving material for use in a silver complex diffusion transfer process comprising an image-receiving layer and containing in a water-permeable layer a hydroquinone developing agent precursor of which at least one of the hydroxyl groups of said hydroquinone has been esterified to form a hydrolyzable aliphatic acyloxy radical comprising a quaternary ammonium group.
 7. A process for forming a visible photographic image comprising treating an exposed photographic element as claimed in claim 1 with an alkaline solution.
 8. A process for forming a visible photographic image comprising treating an exposed photographic element according to claim 1, with an alkaline solution comprising an 1-aryl-3-pyrazolidinone developing agent.
 9. A process according to claim 7, wherein said alkaline solution is an alkaline solution comprising at least one compound selected from sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and borax.
 10. A process for forming a visible photographic image according to the silver complex diffusion transfer process according to which a positive image of an original is obtained by development of an image-wise exposed light-sensitive silver halide material and diffusion of the non-developed complexed silver halide from the emulsion layer of said material to an image-receiving material where the complexed silver halide is converted into a silver containing image in the presence of development nuclei or substances capable of forming such nuclei characterized in that said light-sensitive silver halide material and/or the said image-receiving material comprises a hydroquinone developing agent precursor of which at least one of the hydroxyl groups of said hydroquinone has been esterified to form a hydrolyzable aliphatic acyloxy radical comprising a quaternary ammonium group and in that development is effected by means of an alkaline solution.
 11. A process according to claim 10, wherein said process is carried out in the presence of an 1-aryl-3-pyrazolidinone developing agent.
 12. A process according to claim 10, wherein said alkaline solution is an alkaline solution comprising at least one compound selected from sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and borax. 